The Directory comes from the directory service (#205)

ipx asks ipx-directory on its people's behalf, with the token an admin set
in the new Admin, Directory tab, so the page never talks to it and never
sees the token or a feed's address. /api/directory, /api/popular and a
feed's Directory page answer from it; subscribing takes the address from
the directory and goes through Add feed's steps. With no directory set
up, the Directory says so. The local directory code is gone; its privacy
checks are the snapshot builder's now, and their tests moved with them.

With sharing on, ipx sends its snapshot after every scan, whenever the
config changes (set_cfg) and every half hour: each public feed and how
many here subscribe, never an OPML or Patreon creator itself or anything
private. A feed can be marked private in its settings, for a paid feed
whose address does not give it away; anyone subscribed may mark it, only
an admin unmark it. The admin's category for a feed that names none goes
with it, which the directory uses only while the feed names none, so the
category an admin gives a blog still reaches the Directory.

The directory lists only feeds it has read as a feed: the first snapshot
after a start went before the first scan, when an OPML was not yet known
to be one, and the directory listed the OPML. It now fetches what a
snapshot brings in at once instead of within the minute.

The browser suite runs its own ipx-directory on SQLite; the Directory's
tests match feeds by title, since the directory names them by address.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/directory.md

@@ -9,6 +9,20 @@ one's address: every ipx server still fetches its own feeds.
 This server's is at `https://ipx-dir.sdf1.net`, the `ipx-directory` service of the Arcane project
 `ipx`, with its database `ipx_directory` on the `databases` project's Postgres.
 
+## In ipx
+
+An admin sets it up in **Admin, Directory**: the directory's address, the token its operator gave
+this server, and whether to share. ipx asks the directory on its people's behalf, so the page never
+talks to it and never sees the token or a feed's address. With no directory set up, the Directory
+says so and feeds are added by their address.
+
+With sharing on, ipx sends its snapshot after every scan, whenever the catalogue or these settings
+change, and every half hour: each feed checked at least once, with how many people here subscribe,
+and the category an admin gave a feed that names none. It never sends an OPML or a Patreon creator
+itself (their feeds go instead), or a private feed. A feed's settings have a **Private** switch for
+a paid feed iPX does not recognise by its address; anyone subscribed may turn it on, and only an
+admin off.
+
 ## Tokens
 
 Everything but `/healthz` needs a token, sent as `Authorization: Bearer <token>`. Each one has a
@@ -95,5 +109,6 @@ blocks it, so no snapshot brings it back.
 
 A feed's `id` is the first 64 bits of the SHA-256 of its address, normalised (scheme and host in
 lower case, no default port or fragment), so every server arrives at the same id. `subscribers`
-is the sum over every token's latest snapshot. A feed no snapshot has any more goes. Descriptions
+is the sum over every token's latest snapshot. A feed is listed once the directory has read it as
+a feed, so an OPML or an address that never worked is not, and goes when no snapshot has it any more. Descriptions
 are the feed's own HTML, unsanitized: whoever shows them sanitizes them, as ipx does.